Purified oils and processes of preparing same



Patented Aug. 14, 1951 PURIFIED OILS AND PROCESSES OF PREPARING SAME Fremont P. Pal-kin and George N. Walker, Minneapolis, Minn., assignors to Minnesota, Paints, Inc., a corporation of Minnesota No Drawing. Application May 12, 1947, Serial No. 747,582

Claims. 1

This-invention relates to methods of purifying natural vegetable seed oils and to the resulting purified products, and more particularly to methods of purifying linseed oil, cottonseed oil, corn oil andthe like, and the resulting purified oils.

' The-present application is a continuation-inpart of our application entitled Winterizing Vegetable Oils, Serial No. 505,816, filed October 1 1*, 1943, now Patent No. 2,425,001.

Natural vegetable seed oils are composed of mixtures of many naturally produced chemical compounds including not onl the oily constituents, but also usually, small percentages of natural phosphatides, vegetable waxes, pigments, free fatty acids, and many other compounds. The oily constituents, namely the glyceride esters of long chain fatty acids of the saturated and unsaturated types make. up the largest fraction of vegetable oils, and such materials, to a large extent, determine the properties of the oil, but the remaining constituents also exert a marked and sometimes detrimental effect, depending upon the use to which the oil is put.

Thus, linseed oil contains as its major constituents the glyceride esters of oleic, linolic and linolenic acid, these being chiefly responsible for the drying property of th oil. In addition, as minor constituents, linseed. oil includes natural phosphatides, free fatty acids, vegetable waxes, and other factors not yet identified, together with pigmenting constituents, some or all of which apparently are responsible for the tendency. of' some linseed oils to remain tackey and not dry appropriately,

Natural vegetable oils of commercial grades such as linseed oil, cottonseed. oil, soyabean oil, peanut oil and corn oil become cloudy when they are returned to ordinary (room) temperatures, after having been chilled or cooled to somewhat lower temperatures. The cloudiness may be followed by a settling out'of an. opaque layer, a particularly disadvantageous occurrence when the oil is packaged in glass-and where clarity and brightness are of importance.

In our application above identified we have set forth: the process of removing various undesirable minor constituents of suchnatural vegetable oils such; that the resultant processed oils are brighter and resist the formation of cloudiness on cooling, and in the case of drying and semi-drying oils, the variousproperties are improved. Thus, oils treated. in accordance with that application are enerally somewhat lighter in color and have been winterized.v According to that application the oil is subjected tochilling to a temperature below 60 F. and preferably to a temperature within the lit.

2 range of 20 F. to 50? F. The oils were then allowed to'stand at this low temperature for periods ranging from 24 to 48 hours and in some cases as long as four days to a week, depending upon the temperature and the particular oil. After the oil has been preliminarily chilled to cause the formation of a cloud-forming precipitate, it is further processed by adding thereto a small amount of Water or other electrolyte such as an aqueous solution of inorganic salts, after which the water and the oil are thoroughly mixed and may be allowed to stand. The precipitated material may then be removed eitherby allowing it to settle out, or it may be centrifuged.

According tothat process it will be apparent that considerable periods of time are involved necessitating extensive storage capacity for holding the oil for the time periods involved.

It has now been found that itis possible materiall to speed up the process of our prior application without sacrificing any of the benefits thereof. More" particularly, it has been found that it is possible to convert the previous batch process to a continuous operation and at the same time reduce the time period that any given quantity of oil is subjected to processing.

It has also been found that the removal of constituents which form cloudiness in the oil at low temperatures (Winterizing) can, if desired, be

Winterizing vegetable oils. It is another object of the present invention to provide a continuous process of simultaneously refining and Winterizingvegetable oils.

According to our invention the oil may be chilled rapidly in stream flow for a very short period of time and thereafter mixed with various aqueousrefining agents, after which the precipitated impurities may be removed by centrifuging.

In general the temperatures set forth in our prior application are also suitable for this process. Thus, in general, temperatures of 20 F. to 50 F. have been found satisfactory. For linseed, soyabean, corn and peanut oils the preferred range of temperatures includes 20 F. to 40 F., whereas for cottonseed oil the preferred range is 20 F. to 50 F. Lower temperatures in general arenot. objectionable, but usually entail greater expense from the standpoint of refrigeration and also, in some instances, cause. solidification of the oil,

thereby rendering handling difiicult.

Any means of rapidly reducing the temperature of the oil may be employed. A suitable device for this purpose is the Votator manufactured by the Girdler Corporation. This apparatus effects a rapid transfer of heat from the oil and results in quick continuous chilling of the oil. In operation, it is preferred to feed oil to the refrigerating device through a variable speed pump which makes possible a controlled delivery of oil. The oil may be at a temperature of around room temperature as it enters the refri erating device and may be reduced thereby to the temperatures indicated above. Then, without permitting the oil to become warm and without any reheating, the chilled oil is passed to a small mixing chamber in which water or other aqueous refining agent or an aqueous alkali solution refining agent is added in a proportioned stream. A suitable mixing chamber may consist of a small tank around 30 inches in diameter equipped with a pair of half horsepower mixers. The oil in the mixing chamber may be maintained at a level of about 30 inches. In the mixing chamber the oil and aqueous refining agent, which preferably is chilled to approximately the temperature of the oil, are thoroughly agitated and a stream of the mixture is continuously withdrawn from the mixing chamber and without reheating the oil-refining agent mixture and without permitting it to become warm, the mixture is passed to a centrifuge where the precipitated materials in the oil are separated. After the oil leaves the centrifuge it may contain a minor quantity of impurities, including a small amount of water. The impurities may be removed by washing and/or drying.

The centrifuged and dried oil is bright and clear and resists cloud-formation upon long standing. In the case of linseed oil, the initial starting oil has a yellow color with a slight greygreen tinge and a cloud-precipitate forms upon chilling and then standing at ordinary temperatures as heretofore described. When purified in accordance with the foregoing procedure, the

oil loses some of its color and is bright, perfectly I transparent and remains so after many months standing at ordinary temperatures. Furthermore, no cloud-precipitate forms when the oil returns to normal temperatures after it has been chilled to the temperature of melting ice overnight, or even after chilling to solidification temperatures. There is no settling during storage or when packaged, and the entire portion of the oil is accordingly usable in paint and varnish making techniques, whereas heretofore when linseed oil was allowed to stand in tanks, drums or containers an unusable residue settled therein.

The sludge recovered from the oil constitutes a valuable by-product containing the natural vegetable phosphatides, vegetable waxes and pigments. In the case of linseed oil, and where the sludge is separated by centrifugal methods, the sludge is a greyish-green, soft, somewhat jellylike mass having a viscosity such that it will run at room temperatures 65-'70 F. It may be dehydrated by vacuum desiccation to remove some or all of the contained water, as desired, and serves as a starting material for the preparation of purified constituents of the sludge.

The vegetable oils purified in accordance with the foregoing methods are appreciably less hydrophilic than the corresponding unpurified oils. Thus, linseed oil, purified as herein described, when worked up as paint or varnish, exhibits remarkably improved resistance to water absorp- 4 tion. A paint or varnish compounded of linseed oil purified in accordance with the invention is resistant to water absorption and result ant tackiness and dries harder and quicker and with higher gloss than when oil, not so purified, is used. This is probably due to the fact that the hydrophilic compounds, including phosphatides, vegetable waxes and pigments were removed and hence do not serve to invite the absorption of water in the film. Cottonseed oil, purified in accordance with the invention, is bright and remains perfectly clear for long periods during storage, particularly when stored under cool or chilled conditions. The color of the oil (as distinguished from cloudiness) depends upon the bleaching treatment given the oil. Thus, oils may be bleached successfully, but the cloudforming propensity depends upon whether or not the oils have been treated as herein provided. Cottonseed oil treated in accordance with this invention resists the formation of cloudiness when chilled and then allowed to resume room temperatures. The resultant winterized cottonseed oil, after it has been alkali refined and deodorized, is admirably suitable for human consumption as salad oil or the like. In cottonseed oil of the prior art, a precipitate forms and settles unless the oil has been subjected to an expensive Winterizing process. Cloud formation in cottonseed oil is particularly objectionable because the oil is edible and is frequently packaged in glass, where the precipitate is easily visible to the user.

Corn oil, peanut oil, soyabean oil and other vegetable seed, nut and fruit oils are similarly benefited. The following examples will serve to illustrate the invention but are not to be con-- strued as limitations thereon:

Example I Raw linseed oil was pumped from a supply tank with a variable speed pump through aVVotator at the rate of 75 pounds per minute; The temperature ofthe oil in the supply tank was 15F, while the temperature of the oil leaving the cooler was 30 F. The oil from the cooler was introduced into the mixing chamber where water was added at the rate of 1% pounds per minute. In the mixing chamber the oil was thoroughly agitated. From the mixer a stream of the oil and precipitated material was passed directly and without reheating or warming to a centrifuge where the precipitated material was separated from the oil. The temperature of the oil as it left the centrifuge was 4:8 F. 'The oil was then dried by heating to remove the residual amount of water. The oil thus processed showed only a traceof foots as measured by the A. S. T. M. foots test, both hot and cold. Even when the oil was chilled to the point of complete solidifi-- cation it became bright and clear again when re-warmed to room temperature.

Example II Commercial raw soyabean oil was processed similarly to Example I, except that the oil was pumped at the rate of 70 pounds perminute. The temperature of the oil as it left the cooler was 30 F. In the mixer water was added at the rate of 2 pounds per minute. Theoil was thenmixed, centrifuged and dried as in the previous example. A sample of the oil thus produced became bright and clear at room temperature after having been chilled to 20 F. overnight. 1

. Example. III

Raw linseed oil was passed through the cooler at the rate of 75 pounds per minute, whereupon its temperature was reduced to 30 F. The oil was then passed to the mixer where a solution containing 2 by weight calcium chloride and 4% by weight concentrated hydrochloric acid was added at the rate of two pounds per minute. The oil was then centrifuged without warming, dried by heating and bleached with 1% bleaching clay. The processed oil showed only a trace of foots by both the hot and cold A. S. T. M. foots test, became clear at room temperature after having been cooled overnight to 20 F. and showed no break or cloud on being heated to 600 F.

Example IV Raw linseed oil was pumped from a supply tank through a Votator to a mixing tank. The temperature of the oil coming to the mixing tank was 20 F. A caustic soda solution was added to the oil pumped to the mixing tank. The caustic solution was added at a rate to add 0.5% solid caustic to the oil pumped to the mixing tank. The mixed oil and caustic solution was withdrawn through a bottom outlet in the mixing tank at a rate which maintained a constant level in the tank and was fed to a centrifuge where a separation of the soap stock and oil took place. A 10% caustic soda solution was used so as to give a soap stock which could be easily discharged from the centrifuge.

An average time of six minutes was required for the oil to pass through the system from the time itv entered the Votator until it left the centrifuge,

The treated oil was washed, dried and bleached. The resultant oil had an acid value on the treated oil below 0.1, and did not break when heated to 600 F. in a varnish kettle. Furthermore, the oil did not become cloudy at temperatures below 30 F. or when chilled to solidification and then allowed to return to room temperature.

The processes of alkali refining and winterizing to remove low temperature crystallization material from the oil are combined in one continuous operation in this example.

The refining agents which may be employed in the present invention include water, aqueous solutions of electrolytes, such as acids, alkalis and inorganic solvents. It is possible, therefore, to produce any desired type of refining, either a straight water refining, an acid refining or alkali refining. Simultaneously, with this refining there is accomplished a Winterizing. Usually the refining agent may be employed in a quantity of /2% to 5% or in quantities usually employed for corresponding refining treatments.

It should be stressed that the temperature of the oil after chilling and the addition of the refining agent should not be permitted to rise appreciably inasmuch as materially increased temperatures may effect redissolving of some of the precipitated material. Generally, the temperature should not be allowed materially to exceed 60 F. The redissolving requires a temperature generally somewhat higher and a time period somewhat longer than the temperature and time periods causing precipitation. In general, therefore, where the oil is centrifuged rapidly following precipitation temperatures not substantially in excess of 60 F. are satisfactory, although it is preferred to keep the temperature as close to the refining temperature as possible.

While various embodiments of the invention 6. have been described, it is. to. be understood that the invention is not limited thereto but may be varied within the scope of the following claims:

What we claim is:

1. Process of purifying natural vegetable oils for simultaneously removing the hydrophilic and waxy components thereof which comprises continuously chilling a stream of such oil to a temperature within the approximate range of 20 F. to 50 F; to produce a cloudy precipitate therein, maintaining the thus chilled oil at a tempera ture within said approximate range to prevent the cloudy precipitate from redissolving inthe oil, adding to said chilled oil an aqueous refining agent capable of producing foots, thoroughly mixing the oil and the aqueous refining agent and centrifuging the oil at a temperature not substantially in excess of 60 F. to separate the precipitated cloudy material, the entire process being carried out within a few minutes.

' 2. The process of claim 1 further characterized in that the aqueous refining agent is a water solution of alkali.

3. The process of claim 2 further characterized in that the alkali is sodium hydroxide.

4. Process of purifying natural vegetable oils for simultaneously removing the hydrophilic and waxy components thereof which comprises continuously chilling a stream of such oil to a temperature within the approximate range of 20 F. to F. to produce a cloudy precipitate therein, maintaining the thus chilled oil at a temperature within said approximate range to prevent the cloudy precipitate from redissolving in the oil, adding to said chilled oil an aqueous refining agent-capable of producing foots in an amount within the approximate range of /2% to thoroughly mixing the oil and the aqueous refining agent and centrifuging the oil at a temperature within said approximate range to separate the precipitated cloudy material, the entire process being carried out within a few minutes.

5. Process of purifying natural vegetable oils for simultaneously removing the hydrophilic and waxy components thereof which comprises continuously chilling a stream of such oil to a temperature within the approximate range of 20 F. to 50 F. to produce a cloudy precipitate therein, maintaining the thus chilled oil at a temperature within said approximate range to prevent the. cloudy precipitate from redissolving in the oil, adding to said chilled oil an aqueous alkaline refining agent capable of producing foots, thoroughly mixing the oil and the aqueous alkaline refining agent and centrifuging the oil at a temperature within said approximate range to separate the precipitated cloudy material, the entire process being carried out within a few minutes.

6. Process of purifying natural vegetable oils for simultaneously removing the hydrophilic and waxy components thereof which comprises continuously chilling a stream of such oil to a temperature within the approximate range of 20 F. to 50 F. to produce a cloudy precipitate therein, maintaining the thus chilled oil at a temperature within said approximate range to prevent the cloudy precipitate from redissolving in the oil, adding to said chilled oil an aqueous acid refining agent capable of producing foots, thoroughly mixing the oil and the aqueous refining agent and centrifuging the oil at a temperature within said approximate range to separate the precipitated cloudy material, the entire process being carried out within a few minutes.

'7.- Piocess ofcpurifying linseed oil for simultaheously removing the hydrophilic and waxy components thereof which comprises continuously chilling a stream of such oil to a temperature within the approximate range of 20 F. to 50 F. to produce a cloudy precipitate therein, maintaining the thus chilled oil at a temperature Within said approximate range to prevent the cloudy precipitate from re-dissolving in the oil, adding to said chilled oil an aqueous refiim'ng agent capable of producing foots, thoroughly mixing the oil and the aqueous refining agent and centrifuging the oil at a temperature within said approximate range to separate the precipitated cloudy material, the entire process being carried out within a few minutes.

8. Process of purifying soyabean oil for simultaneously removing the hydrophilic and waxy components thereof which comprises continuously chilling a stream of such oil to a temperature within the approximate range of 20 F. to 50 F. to produce a cloudy precipitate therein, maintaining the thus chilled oil at a temperature within said approximate range to prevent the cloudy precipitate from re-dissolving in the oil, adding to said chilled oil an aqueous refining agent capable'of producing foots, thoroughly mixing the oil and the aqueous refining agent and centrifuging the oil at a temperature within said approximate range to separate the precipitated cloudy material, the entire process being carried out Within a few minutes.

9. Process of purifying natural vegetable oils for simultaneously removing the hydrophilic and Waxy components thereof which comprises con- 3.,

tinuously chilling a stream of such oil to a temperature within the approximate range of 20 F.

to 50 F. in a time'period of a few seconds, passing said stream of oil to a mixing zone, continuously introducing into said mixing zone a proportioned stream of an aqueous refining agent capable of producing foots, intimately mixing the aqueous refining agent and the oil in said mixin zone while maintaining the temperature thereof within said approximate range, continuously Withdrawing a stream of said mixture and centrifuging said mixture at a temperature not substantially in excess of 60 F. for separation of the precipitated cloudy material.

10. The process of purifying a natural vegetable oil having drying characteristics which com prises continuously chilling a stream of said oil to a temperature of approximately 30 F. to produce a cloudy precipitate therein, maintaining the chilled oil at approximately said temperature while mixing therewith an aqueous refining agent capable of producing foots, thoroughly mixing the aqueous refining agent with the oil and continu: ously centrifugally separating the cloudy precipitate from the oil While maintaining the temperature of the oil near said approximate temperature, the entire process being carried out Within a few minutes.

FREMONT P. PARKIN. GEORGE N. WALKER.

REFERENCES CITED Ihe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,223,077 Stadt Nov. 26, 1940' 2,425,001 Parkin et a1 Aug. 5. 1947 

1. PROCESS OF PURIFYING NATURAL VEGETABLE OILS FOR SIMULTANEOUSLY REMOVING THE HYDROPHILIC AND WAXY COMPONENTS THEREOF WHICH COMPRISES CONTINUOUSLY CHILLING A STEAM OF SUCH OIL TO A TEMPERATURE WITHIN THE APPROXIMATE RANGE OF 20* F. TO 50* F. TO PRODUCE A CLOUDY PRECIPITATE THEREIN, MAINTAINING THE THUS CHILLED OIL AT A TEMPERATURE WITHIN SAID APPROXIMATE RANGE TO PREVENT THE CLOUDY PRECIPITATE FROM REDISSOLVING IN THE OIL, ADDING TO SAID CHILLED OIL AN QUEOUS REFINING AGENT CAPABLE OF PRODUCING FOOTS, THOROUGHLY MIXING THE OIL AND THE AQUEOUS REFINING AGENT AND CENTRIFUGING THE OIL AT A TEMPERATURE NOT SUBSTANTIALLY IN EXCESS OF 60* F. TO SEPARATE THE PRECIPITATED CLOUDY MATERIAL, THE ENTIRE PROCESS BEING CARRIED OUT WITHIN A FEW MINUTES. 